Papain is to use biological engineering plants from papaya immature fruit extract of biological products and natural, it is composed of 212 amino acids, molecular weight for 21000, belong to contain sulphur (SH) peptide chain enzymes, has the protease and ester of the enzyme activity, and have a wide range of specificity, protein, polypeptide of plants and animals,esters,amides,etc have strong ability of enzyme solution, but also has the ability of synthesis, the protein hydrolysis content to synthesize protein kind material,this ability can be used to improve plant and animal protein nutritional value of nature.